Both Aristotle and Ernst Mayr present theories of dual explanation in biology, with proximal, clearly physical explanations and more distal, biology-specific explanations. Aristotle’s presentation of final cause explanations in Posterior Analytics (II.11) relates final causes to the necessary material, formal, and efficient causes that mediate them. Johnson (Aristotle on teleology, 2005) and Leunissen (Apeiron 43:117–142, 2010b) demonstrate the problematic nature of historical and recent interpretations and open the door for a new interpretation consistent with modern evolutionary theory. Mayr’s (Science 134:1501–1506, 1961) differentiation of proximate and ultimate/evolutionary causes provides a key to appropriating Aristotle for modern use, if care is taken to differentiate Mayr’s proximate/distal and mechanical/evolutionary distinctions from his intentional/non-intentional distinction. Building on Mayr, and noting his appropriation of ancient and recent commentary, a strong case can be made for nested explanation, wherein evolutionary explanations are instantiated in systems of mechanical explanations. Biological concepts of organism, gene, function, etc., are etiologically prior to mechanical explanations of function, but temporally posterior to mechanical explanations of historical adaptation. Such an analysis sheds light on recent arguments within evolutionary biology while highlighting the importance of epistemology in contemporary science.